1. Field of the Invention
The present invention relates to a sheet processing apparatus and an image processing system. More specifically, the present invention relates to an additional folding mechanism for reinforcing a fold line portion of a center-folded sheet bundle consisting of paper sheets, etc.
2. Description of the Related Art
Sheet such as a paper sheet and the like printed by an image forming apparatus, such as a copying machine, printer, or printing machine, is discharged from the image forming apparatus in some cases, and in other cases, a predetermined number of the printed sheets are bundled, then the sheet bundle is stitched in its center, and then the stitched sheet bundle undergoes center-folding processing for folding the sheet bundle in the center to be bundled into a booklet.
On the other hand, a conventional method has been known in which, in order to reinforce a fold line in a center-folded portion of a booklet constituted by a saddle-stitched sheet bundle, an additional folding operation for pressing the fold line portion is performed by using a roller which moves along the spine of the booklet.
For the additional folding operation, a configuration has been known in which a roller with a shaft axially directed in a direction perpendicular to the orientation of the fold line of a booklet presses the fold line portion while moving in a direction parallel to the orientation of the fold line.
For an additional folding unit used in an additional folding operation, a configuration has been employed in which an additional folding unit reciprocates in the widthwise direction of folded sheet bundle in accordance with the width of a maximum sheet size (e.g., see Japanese Patent Application Laid-open No. 2012-20882).
More specifically, a position on the side of one edge of the folded sheet bundle in the widthwise direction is previously set as a standby position for an additional folding unit, and the additional folding operation is performed in a forward motion for moving the additional folding unit from its standby position along the widthwise direction of the folded sheet bundle, while in a backward motion, the additional folding unit returns to its standby position.
In a conventional additional folding mechanism, time required for the additional folding mechanism to come back to the standby position after the additional folding from the standby position is completed may be determined in proportion to the sheet width. In other words, in a conventional configuration in which the standby position is set on the side of one edge of the folded sheet bundle in the widthwise direction, the same time as time required in completing an additional folding operation is also required to return the additional folding mechanism back to the standby position.
Accordingly, because operating time not directly related to the additional folding operation is required, a problem may arise such that the efficiency of the additional folding operation, particularly the additional folding operation performed on serially fed folded sheet bundles, becomes low.
In consideration of the above-described problem arising in conventional sheet processing apparatuses, there is a need to provide a sheet processing apparatus including a configuration capable of improving the working efficiency.